darktable colour management has been working fine for my raw files (dt 2.6 for Windows). Today I was doing some colour management tests on the basis of this DisplayCal page. To my surprise, darktable failed the “Test No. 2: Color Management with LUT-based profiles”. Here’s a screenshot:
You can see that dt has a problem with both LUT-based jpegs (with and without the matrix profile). Also, the thumbnails in the filmstrip and in lighttable don’t respect the embedded profiles (despite being told in the Preferences to colour-manage thumbnails and to use LittleCMS).
I might add that these same jpeg files passed the test in the following applications: Firefox 64, RawTherapee 5.5, Lightroom 5, DxO PhotoLab2, Photoshop Elements 12, Affinity Photo 1.6.5, XnViewMP 0.9.2, FastRawViewer 1.4.11.
The latest version of FastPictureViewer failed the LUT-only file but the LUT+matrix showed fine. The same happened with Windows Photo Viewer.
The only other raw converter which failed this test besides darktable was Capture One Express for Sony v.12.
I have an old version of C1 which also has problems with LUT-profiles. It messes up the blackpoint I think. It works fine with curves-based profiles though. The same issue occurs with the Olympus Viewer. I would not be suprized if Phase1 had not fixed this bug yet. Some apps just don’t like LUT-profiles. Have not done the Displaycal test yet though.
But darktable should be able to deal with LUT-profiles.
What’s strange with C1 is that the thumbnails show fine in the import dialogue but fail the test after the import. I remember doing a similar test a couple of years ago and the results were similar.
I agree, dt should be able to deal with this just fine – XnViewMP, which is also based on LittleCMS, doesn’t have a problem with the test.
I downloaded the zip-file and opened the files with dt and RawTherapee. I am a little confused about this test, however the results are very different in the two programs. RT shows that the profile is used, dt shows that the profile is not used except for one picture where there is a fallback matrix. So I think yes you are right. However, I think I tested this some time ago and realized that dt is indeed not using LUT-profiles.
I did not change any profiles in my system settings. Just used my “regular” display profiles.
Also I think I must check what kind of display profile I use (LUT? curves?). I honestly have no idea in this moment.
I am trying to help but unfortunately I am not a developer who really knows what is going on in dt color management. There should be someone else here who is smarter than I.
Thanks, this at least confirms that it’s not a Windows-related issue since your screenshot suggests you viewed the photos in a Linux version of dt.
I switched my monitor profile from LUT/matrix to 1-curve matrix but it helped neither dt nor C1.
It’s not such a big deal because people will not normally use jpegs/tiffs with LUT-based profiles, but it’s interesting that the vast majority of colour-managed programs have no problem with such files.
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